Local muscle training improves exercise capacity in CHF patients
MedWire News: Exercise training aimed at improving small muscle mass - as opposed to whole-body exercise - is a "powerful" way to improve exercise tolerance in people with chronic heart failure (CHF), research suggests.
The study, published in the Journal of the American College of Cardiology, found that an 8-week program of knee-extensor exercise offered "clear improvements" in muscle structure and oxygen utilization.
"These mechanistic findings may have important practical consequences in terms of guiding future pharmacological rehabilitative interventions in this population," write Fabio Esposito (University of Milan, Italy) and co-authors.
Cardiac rehabilitation traditionally employs whole-body exercise, which challenges large muscle mass and therefore taxes the central circulation. This approach is effective in improving exercise capacity in patients with CHF but the relative contributions of central hemodynamic and peripheral responses are unclear.
To investigate, Esposito's group enrolled six men with clinically stable CHF and six healthy male volunteers matched for age and physical activity. Each participant was assessed before and after completing a supervised program of knee-extensor exercise training.
The exercise entailed three 50-minute sessions per leg per week of cycle exercise, during which the ankle of one leg was attached by a rigid bar to a cycle ergometer. The overall intensity was increased progressively over a period of 8 weeks.
At baseline, peak oxygen uptake in the femoral vein was significantly lower in CHF patients than in controls, report the researchers.
In both groups of men, however, knee-extensor exercise training was associated with significant improvements in quadriceps muscle structure (as indicated by increases in capillatory and mitochondrial density).
In men with CHF, the exercise program significantly increased peak oxygen uptake to a level exceeding that seen in healthy men before exercise. Interestingly, the improvement occurred in the absence of any alteration in maximal cardiac output.
Taken together, these observations provide evidence of significant peripheral vascular and metabolic plasticity in CHF patients, "which can be developed in isolation with small muscle mass training and then harnessed to the benefit of whole-body exercise capacity," note the authors.
They conclude: "In the face of continued central limitations, clear improvements in muscle structure, peripheral convective and diffusive oxygen transport, and subsequently, oxygen utilization support the efficacy of local skeletal muscle training as a powerful approach to combat exercise intolerance."
By Joanna Lyford